Could the check engine light and white smoke be due to recent repairs

Look for any obvious leaks once it cools down , maybe the brake reservoir had a loose cap , I'd think if anything smoked it would be be after the initial highway miles . At least it's not fuel , you'd smell that . Something else could have gone wrong by pure coincidence .

It probably is, indirectly, related to the recent repairs. On an older model when repairs are made and other things have to be moved to get to the components being worked on things can happen. Old hoses are stiff and brittle. They can start leaking after being disturbed. Same with old wiring that hasn't been touched since the vehicle was built. That kind of wispy grey smoke looks like something oil based is burning. I'd have it towed back to the shop for a second look. Or use a mobile mechanic, whichever is better for you. I wouldn't drive it until you find out what's going on. The last thing you want is a fire!! Hope that helps! Jim